JPS6385943A - Control system for data deletion in read only memory device - Google Patents

Abstract

PURPOSE:To keep the secrecy of a deleted data in a read only data memory medium, by providing a file state storing means which represents whether a file is deleted or not, and a data deleting means which rewrites a dummy data compulsorily for the deleting request of the file, and writes a bit of information in the file state storing means. CONSTITUTION:The read only data memory medium 1 is divided into a label storing area 2, and a data storing area 4. In the label storing area 2, a label 3 including a bit of managing information is written at the time of generating the file 5, and a deleting label 11 is written at the time of deleting the data by a label deleting means 9. In the data storing area 4, the file 5 is stored, and a file state memory part 6 which represents whether the data of the file 5 is already deleted or not, and a data area 7 in which the file 5 is written, are provided. The file deleting means 9 starts up the data deleting means 10 at the time of deleting the data. The data deleting means 10 writes the dummy data compulsorily in the data area 7 of the file 5 at the time of deleting the data, and disables the reading of the data written previously, and also, writes a bit of information to represent the fact in the file state memory part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data erasure control method for a non-rewritable storage device, and particularly to a data erasure control method for a storage device equipped with a non-rewritable data storage medium [conventional method] [Technology] Conventionally, the file deletion method for this type of non-rewritable storage device is to add a deletion label to the label storage area to indicate that the file has been deleted when a file deletion request is made, and then delete the file. The method was to do so.

[Problem that the invention seeks to solve]

In the conventional file deletion method for non-rewritable storage devices described above, the presence or absence of a file is controlled based on the presence or absence of a deletion label. If the data is directly accessed without going through it, the data in the file that should have been deleted can be referenced, which has the disadvantage that confidentiality cannot be protected.

In view of the above-mentioned points, it is an object of the present invention to refer to the data of a deleted file even when it is determined that the file exists due to a failure in reading the deletion label due to a failure, or when the data is directly accessed without going through the file label. An object of the present invention is to provide a data deletion control method for a non-rewritable storage device that prevents data deletion from being performed.

[Means for solving problems]

The data erasure control method for a non-rewritable storage device of the present invention includes a non-rewritable data storage medium,
The storage area on the α medium is divided into a label storage area and a data storage area, and when a file is created, the file data is written to the data storage area, and a label containing file management information is added to the label storage area. In a non-rewritable storage device, a deletion label indicating that the file has been deleted is added to the label storage area when the file is deleted, and the file status memory is provided in the file and indicates whether the data has been deleted. and means for forcibly rewriting dummy data in the data area of the file when a file deletion request is made, making the previously written data unreadable, and writing a message to the effect in the file status storage means. and data erasing means for writing the information.

[Effect]

In the data erasure control method for a non-rewritable storage device of the present invention, the file status storage means provided in the file indicates whether the data has been erased, and the data erasure means indicates whether the file deletion request is made. When this happens, dummy data is forcibly rewritten in the data area of the file to make the previously written data unreadable, and information to that effect is written in the file status storage means.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The data erasure control method of the non-rewritable storage device of this embodiment is as follows:
A non-rewritable data storage medium 1, a file oven means 8, a file deletion means 9, and a data erasure means 10
Its main parts are composed of:

A non-rewritable data storage medium 1 has a label storage area 2.
and a data storage area 4.

In the label storage area 2, a label 3 including management information of the file 5 is written when the file 5 is created, and
When the file 5 is deleted, a deletion label 11 is written by the file deletion means 9.

A file 5 is stored in the data storage area 4, and within the file 5 there is a file status storage section 6 that indicates whether the data of the file 5 has been deleted, and a data area 7 in which the data of the file 5 is written. and is provided.

The file oven means 8 is capable of controlling access to the file 5 by determining whether the file 5 has been deleted based on the deletion label 11 or the file status storage unit 6.

The file deletion means 9 activates the data deletion means 10 when deleting the file 5, and additionally writes the deletion label 11 in the label storage area 2 after the operation of the data deletion means 10 is completed.

The data erasing means 10 forcibly rewrites dummy data into the data area 7 of the file 5 when deleting the file 5 to make the previously written data unreadable, and also stores the data in the file status storage unit 6. Write information to that effect.

Next, the operation of the data erasure control system of the non-rewritable storage device of this embodiment configured as described above will be explained with reference to FIGS. 2 and 3.

First, a case will be described in which the file 5 is deleted from the written state shown in FIG. 2.

The user requests the file deletion means 9 to delete the file 5 and activates the file deletion means 9.

The activated file deletion means 9 searches the label storage area 2 to find the label 3 of the file 5 to be deleted from the non-rewritable data storage medium l. When the label 3 of the file 5 is found, the file deletion means 9 obtains the position information of the file 5 from the label 3 and activates the data deletion means 10.

The activated data deletion means 10 is the file deletion means 9
File 5 based on the location information of file 5 passed from
Reads the file status storage unit 6 in the file and returns it to an unwritten state (
Detect whether the data is alive (B).

When it is detected that the file state storage unit 6 is in an unwritten state, the data erasing means 10 forcibly rewrites dummy data to the data area 7 of the file 5, as shown in FIG. The data written earlier is made unreadable, and then information indicating that the data has been deleted is written to the file status storage section 6, and control is returned to the file deletion means 9.

The file deletion means 9 whose control has been returned adds a deletion label 11 indicating deletion of the file 5 in the label storage area 2 and completes the file deletion process.

Next, a case will be described in which the deleted file 5 deleted in this manner is accessed.

When the user activates the file oven means 8 to access the file 5, the activated file oven means 8 searches the label storage area 2 for the label 3 and deletion label 11 of the file 5 to be accessed.

When deletion label 11 of file 5 is searched,
File oven means 8 is searched deletion label 11
It is recognized that file 5 is a deleted file, and the user is notified of this fact.

If the deletion label 11 of the file 5 is not searched, the file oven means 8 deletes the searched label 3.
The location information of the file 5 is obtained from the file 5, and the file status storage section 6 of the file 5 is read.

Then, the file oven means 8 detects whether or not information indicating that the data has been deleted is written in the file status storage unit 6, and determines whether the file 5 is a deleted file. . This detection of information in the file status storage unit 6 is performed so that even if the file 5 is not recognized as a deleted file because the deletion label 11 in the label storage area 2 is not searched due to a failure, it can be recognized as a deleted file. done in order to When the file 5 is a deleted file, the file oven means 8 notifies the user to that effect; 1. Data in data area 7 is not accessed.

By the way, if the user directly accesses the deleted file 5 without going through the file oven means 8, it is possible to access the data in the data area 7 of the deleted file 5. However, the data area 7 has been forcibly written with dummy data by the data erasure means 10, and the previously written data has already become unreadable, so even if this dummy data is read, the confidentiality will be leaked. Never.

〔Effect of the invention〕

As explained above, the present invention includes a file status storage means that indicates whether or not a file has been deleted, and a means for forcibly rewriting dummy data in the data area of the file when a file deletion request is made. At the same time, by providing data erasure means that writes information to that effect in the file status storage means, even if reading of the deletion label fails due to a failure or data is directly accessed without going through the file label, This has the effect of protecting the confidentiality of data in deleted files in a non-rewritable data storage medium.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the data erasure control method of the non-rewritable storage WW of the present invention, and FIG. 2 is the state before file deletion by the data erasure control method of the non-rewritable storage device of this embodiment. FIG. 3 is a diagram showing the state of the non-rewritable storage device of this embodiment after file deletion by the data deletion control method. In the figure, ■...Data storage medium that cannot be rewritten, 2...Label storage area, 3...Label, 4...Data storage area, 5...File, 6...File status 7. Data area; 8. File opening means; 9. File deletion means; 10. Data deletion means; 11. Deletion label.

Claims (1)

[Claims] A non-rewritable data storage medium is provided, and a storage area on the data storage medium is divided into a label storage area and a data storage area, and file data is written to the data storage area when a file is created. In the non-rewritable storage device, a label including management information of the file is added to the label storage area, and a deletion label indicating that the file has been deleted when the file is deleted is added to the label storage area. A file status storage means is provided to indicate whether or not data has been deleted, and when a file deletion request is made, dummy data is forcibly rewritten to the data area of the file and the data is written first. 1. A data deletion control method for a non-rewritable storage device, comprising: data deletion means for rendering unreadable data and writing information to that effect in the file status storage means.